Influence of the ears canals location on spherical head model for the individualized interaural time difference

The spatialization rendering with binaural synthesis is still limited by the individualization of the spatial filters, which are usually composed of a pure delay for the interaural time difference (ITD) and a minimumphase filter for the spectral cues. This paper deals with the individualization of the ITD based on physical modeling. Individualized ITDs are well predicted by a spherical-head model with a customized radius derived from an empiric linear combination of three head anthropometric parameters describing the listener’s head. However it can be observed that the constant ITD contours computed from the spherical-head model are concentric circles, whereas the constant ITD contours extracted from measured HRTFs show deviations from these circles, especially for azimuths near to the interaural axis. The location of the ears with respect to the center of the head seems to be the main factor to reproduce these deviations. The authors propose to introduce a parameter governing the ears’ shifting, so as to break the symmetry of the spherical-head model. This idea leads to a new formula for the computation of individualized ITDs. The formula is tested by comparison with measured data. The authors also examine to what extent the deviations of the measured ITD along the circles contribute to the individualization. Psycho-acoustical experiments are performed to answer this question.